查看更多>>摘要：Exploring low-cost,high-performance,and stable electrocatalysts toward the oxygen evolution reaction(OER)is highly desired but remains challenging.Transition metal hydroxide has been wildly utilized as a promising candidate,but practical implementation is impeded by insufficient catalytic activity,easy agglomeration,and poor conductivity.Here,we report that both phosphorization and combination with MXnene can improve the catalysts'intrinsic activity and conductivity.Besides,MXene also prevents the agglomeration of the nanoparticles,resulting in the enhanced exposure of active sites.Experimental char-acterizing and density functional theory simulations revealed that P species can attract electrons to pro-mote the formation of high-valence states of adjacent metal atoms,and coupling MXene support can effectively modulate the electronic structure and optimize the d-band center,which boosts the OER per-formance.Consequently,the optimized NiFeCoP/Mxene catalyst exhibits a low overpotential of 240 mV at a current density of 10 mA cm-2,a small Tafel slope of 55 mV dec-1,and superior long-term stability of 40 h in 1 M KOH electrolyte,which is superior to other counterparts.
Muhammad IsmailHaider AbbasChandreswar MahataChanghwan Choi...
98-107页
查看更多>>摘要：The multilevel storage capability of nonvolatile resistive random access memory(ReRAM)is greatly de-sired to accomplish high functioning memory density.In this study,Ta2O5 thin film with different thick-nesses(2,4,and 6 nm)was exploited as an appropriate interfacial barrier layer for limiting the formation of the interfacial layer between the 10 nm thick sputtering deposited resistive switching(RS)layer and Ta ohmic electrode to improve the switching cycle endurance and uniformity.Results show that lower form-ing voltage,narrow distribution of SET-voltages,good dc switching cycles(103),high pulse endurance(106 cycles),long retention time(104 s at room temperature and 100℃),and reliable multilevel resis-tance states were obtained at an appropriate thickness of～2 nm Ta205 interfacial barrier layer instead of without Ta2O5 and with～4 nm,and～6 nm Ta2O5 barrier layer,ZrO2-based memristive devices.Besides,multilevel resistance states have been scientifically investigated via modulating the compliance current(CC)and RESET-stop voltages,which displays that all of the resistance states were distinct and stayed stable without any considerable deprivation over 104 s retention time and 104 pulse endurance cycles.The l-V characteristics of RESET-stop voltage(from-1.7 to-2.3 V)of HRS are found to be a good linear fit with the Schottky equation.It can be seen that Schottky barrier height rises by increasing the stop-voltage during RESET-operation,resulting in enhancing the data storage memory window(on/off ratio).Moreover,RESET-voltage and CC control of HRS and LRS revealed the physical origin of the RS mecha-nism,which entails the formation and rupture of conducting nanofilaments.It is thoroughly investigated that proper optimization of the barrier layer at the ohmic interface and the switching layer is essential in memristive devices.These results demonstrate that the ZrO2-based memristive device with an optimized～2 nm Ta2O5 barrier layer is a promising candidate for multilevel data storage memory applications.
查看更多>>摘要：Electromagnetic wave absorber is critical for reducing increasingly serious electromagnetic wave pollu-tion,however,the development of lightweight and broadband microwave absorbers remains a pressing challenge.We report here the rational design and synthesis of N-doped Ni@SiO2/graphene composite con-structed from 3D interconnected porous graphene network and Ni@SiO2 core-shell architecture,which fulfills lightweight and broadband requirements while exhibiting highly efficient electromagnetic wave absorption.The porous graphene network,functioning both as lightweight support and dielectric medi-ator,was synthesized via NaCl template-assisted high-temperature calcination method.Upon uniformly attached with core-shell Ni@SiO2 on the surface,the resulting abundant heterogeneous interfaces con-structed by graphene-Ni and Ni-SiO2 strongly reinforce polarization loss.The presence of low dielectric SiO2 allows facile tuning of the complex permittivity of ternary composite by adjusting coating thick-ness to balance the attenuation ability and impedance matching.Moreover,further N-doping of graphene assists in the optimization of dielectric loss ability.Taking account of the advantages arising from the porous hierarchical architecture,multiple absorption centers and diverse interfaces,the lightweight com-posite exhibits an ultra-strong reflection loss(RL)value of-71.13 dB at 13.76 GHz with a thickness of 2.46 mm and broad effective absorption bandwidth of 7.04 GHz at a low filler content of 15 wt.％.More importantly,the effective absorption range covers 13.28 GHz(4.72-18 GHz)with the optimized thickness of 1.6-5 mm,representing 83％of the whole range of frequencies.Our results demonstrate that the novel 3D porous N-doped Ni@SiO2/graphene network with hierarchical architecture is a promising candidate for high-performance electromagnetic wave absorption.
查看更多>>摘要：Recent studies have shown that many challenges encountered in conventional single crystal growth meth-ods,including high production costs,can be overcome by using the solid-state single-crystal growth(SSCG)approach,which has been recognized as a simple and cost-effective alternative for obtaining sin-gle crystals.In this work,Y3Al5O12(YAG)and Nd3+-doped YAG(Nd∶YAG)single crystals were grown via the SSCG method using spark plasma sintering(SPS).The growth of single crystals was initiated at the surface of(110)YAG single-crystal seeds embedded inside YAG and Nd∶YAG powder beds,and this growth continued as the surrounding polycrystalline matrix was converted into a single crystal.The application of external pressure during the SPS process has been found beneficial for reducing the porosity of the grown single crystals.Moreover,high Nd3+doping levels had a positive effect on the conversion kinetics,with a growth rate of almost 50 pm/h,which increased the driving force for single-crystal growth through the solute drag effect.EDS elemental mapping and line scans confirmed the compositional uniformity of the grown single crystals,while EBSD images verified their crystallization in the(110)direction.The ob-tained results confirm the strong potential of the SSCG technique coupled with SPS for the growth of undoped and highly doped YAG single crystals with excellent quality.
查看更多>>摘要：With important application prospects,eutectic high entropy alloys have received extensive attention for their excellent strength and ductility in a large temperature range.The excellent casting characteristics of eutectic high entropy alloys make it possible to achieve well manufacturability of selective laser melting.For the first time,we have achieved crack-free eutectic high entropy alloy fabricated by selective laser melting,which has excellent mechanical properties in a wide temperature range from-196℃to 760℃due to ultra-fine eutectic lamellar spacing of 150-200 nm and lamellar colony of 2-6 μm.Specifically,the room temperature tensile strength exceeds 1400 MPa and the elongation is more than 20％,which significantly improved compared with those manufactured by other techniques with lower cooling rate.
查看更多>>摘要：Defect sites on oxide semiconductors play a crucial role in promoting photocatalytiperformance and mod-ulating the bandgap structure of photocatalysts.However,the role of interfacial coordinatively unsatu-rated defect sites between metal and oxide in photocatalysis is still under debate.So,we designed an experiment to probe the role of interfacial coordinatively unsaturated defect sites.In this work,a se-ries of Ti/TiO2 photocatalysts with varying concentrations of interfacial Ti3+sites were prepared through an epitaxial growth method under hydrothermal conditions.Through experimental and computational investigations,the roles of interfacial defect sites were discussed in detail.On the one hand,the inter-facial coordinatively unsaturated Ti3+sites could act as visible-light-responsive sites in photocatalytic reactions due to the overlap and hybridization of multiple electronic orbitals.On the other hand,the Ti/TiO2 interface exhibited a certain degree of metallic character near the Fermi level because of the par-tial delocalization and redistribution of electrons,facilitating the charge migration and separation across the metal-oxide interface.Consequently,the obtained Ti/TiO2 catalysts showed notably enhanced charge transfer efficiency and visible light photocatalytic activity compared to their pristine counterparts.This work may provide a new perspective to interfacial defect engineering in classic metal/oxide heterojunc-tion photocatalysts and figure a more precise direction to synthesize higher effective photocatalysts for environmental governance.
查看更多>>摘要：Nowadays,the yearning for microwave absorption materials(MAMs)are more and more urgent for deal-ing with the increasingly serious electromagnetic pollution and the demand of modern military security.Among potential candidates,the graphene(GE)based magnetic hybrids have advantages in structural controllable and designing flexibility,providing opportunities for achieving highly efficiency of microwave absorption(MA).Thus,the structural regulation and MA performances of GE-based magnetic hybrids arouse great attention in related fields.In this review,we summarize the recently progress in MA perfor-mance of GE-based magnetic hybrids.Typical absorption process and corresponding mechanism are firstly introduced,for guiding the design of GE-based magnetic MAMs.Then,the magnetic components,syn-thesis methods,structural features and regulation strategies of these GE-related magnetic materials are reviewed,and their influences on MA performances have also been discussed.Challenges,and prospects of the GE-based magnetic MAMs are suggested.This review provides a brief but systematic introduction to GE-based magnetic MAMs,which may pave the way for the design of MAMs with highly efficient MA performances.
查看更多>>摘要：The trade-off between strength and ductility has been an enormous difficulty in the field of materials for an extended time due to their inverse correlation.In this work,friction stir processing(FSP)was for the first time performed to high-strength and high-melting-point Ni-Co based superalloy(GH4068),and enhanced strength and ductility were achieved in FSP samples.At room temperature,the FSP sam-ple demonstrated significantly higher yield strength and ultimate tensile strength(1290 and 1670 MPa)than that of the base material(BM,758 and 904 MPa)and advanced wrought GH4068 alloy(982 and 1291 MPa),concurrent with high tensile ductility(～24％).Compared with the BM,70％higher yield strength of the FSP sample results from the remarkable contribution of grain-boundary and nanotwin strengthening,which has been confirmed by the multimechanistic model studied in this work.More im-portantly,with increasing temperature,an excellent strength-ductility synergy was obtained at 400℃,i.e.,the yield strength of the FSP sample was increased by more than 50％compared with the BM(from 789 to 1219 MPa);more interestingly,the elongation was also significantly increased from 17.9％in the BM to 28.5％in the FSP sample.Meanwhile,the Portevin-Le Chatelier effect was observed in the engi-neering stress-strain curve.The occurrence of this effect may be attributed to the interaction between solutes and defects like twins and mobile dislocations.Moreover,the grain refinement mechanism of FSP samples was proved to be discontinuous dynamic recrystallization.
查看更多>>摘要：Cold spray(CS)is considered as a new type of repairing technique for restoration or remanufacturing of a wide range of unserviceable engineering components due to its unique'cold'characteristic.In this work,a viable repairing approach i.e."cold spraying followed by hot rolling post-treatment"was suc-cessfully applied to restore defective neutron shielding B4C/6061 Al composite plates.Scanning electron microscopy(SEM)and electron backscatter diffraction(EBSD)results revealed that the coating-substrate interface is in a good bonding state without micro-cracks.Hot rolling post-treatment resulted in improved microstructure of the as-sprayed deposit with more uniform distribution of B4C particles in the matrix.Moreover,well bonded splat boundaries and strain free Al grains were evolved in the matrix due to enhanced splat deformation and continuous dynamic recrystallization(CDRX).Three-point bending test results revealed that the strength of the repaired material is at par with the in-service plates.The find-ings of this work could be considered as a great stride to further extend possible applications of CS for repairing engineering structural components.
NETL
NSTL
维普
万方数据